1. Field
The present invention relates to a battery charging method and a battery management system therefor.
2. Description of the Related Art
Recently, as technology for portable devices, such as portable computers, mobile phones or cameras, is developed and demand for the portable devices is increased, demand for secondary batteries as an energy source is also increasing rapidly.
Because the secondary battery is rechargeable, it may be continuously used by recharging even though the battery has been discharged. Thus, the secondary battery varies in performance depending on the state of charge. Therefore, efforts have been made to improve the charging method and thereby enhance the performance of the secondary battery.
FIG. 1 is a diagram showing a constant current/constant voltage charging method (hereinafter, referred to as a CCCV method), which is one of the comparable methods of charging the secondary battery. FIG. 1 shows changes in voltage and temperature when a charging operation is performed under the control of current as shown in the drawing. At an initial charging stage, first, constant current (CC) charging is performed. That is, assuming that a current value of the battery, which requires one hour to change from a full charge state to a discharge state, is 1 C-rate, charging is performed with the constant current of about 0.5 C-rate, for example. Until the voltage is increased by the charging operation to reach a preset voltage Vc, e.g. 4.2V, the CC charging is continued. When the voltage reaches the preset voltage Vc, the charging operation is switched to constant voltage (CV) charging. Thereby, the charging operation is performed while a charging current is reduced, so as to maintain the preset voltage Vc.
In order to achieve fast charging in the CCCV charging method, the C-rate of the CC charging should be set to a large value. However, the higher the C-rate is, the greater the heat dissipation and the rate of degradation of the secondary battery may be. Consequently, the output and capacity of the secondary battery may be undesirably reduced.